Alkaline fuel cells (AFC) are known as a fuel cell that operates at a relatively low temperature (for example, less than or equal to 250 degrees C.). Various liquid fuels or gaseous fuels can be used in an AFC and for example, use of methanol as a fuel causes the following electrochemical reaction.Anode: CH3OH+6OH−→6e−+CO2+5H2OCathode: 3/2O2+3H2O+6e−→6OH−Overall: CH3OH+3/2O2→CO2+2H2O
In this context, Japanese Patent Application Laid-Open No. 2016-071948 proposes a solid alkaline fuel cell in which an inorganic solid electrolyte that exhibits hydroxide ion conductivity is configured as a layered double hydroxide (LDH) that does not exhibit liquid permeability and gas permeability.
LDH is expressed by the general formula [M2+1-xM3+x(OH)2] [An−x/n.mH2O] (wherein M2+ is a divalent cation, M3+ is a trivalent cation, and An− is an n-valent anion).
LDH has a layered structure in which anions and water that correspond to the second half of the above general formula are retained between double hydroxide layers that correspond to the first half of the general formula. A double hydroxide layer is configured as a solid solution of trivalent metal ions in a divalent metal hydroxide and exhibits a positive charge. The anions between the layers exhibit a negative charge to thereby compensate for the positive charge of the double hydroxide layer.